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.TH INDEX 3C "Jul 24, 2002"
.SH NAME
index, rindex \- string operations
.SH SYNOPSIS
.LP
.nf
#include <strings.h>

\fBchar *\fR\fBindex\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
.fi

.LP
.nf
\fBchar *\fR\fBrindex\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBindex()\fR and \fBrindex()\fR functions operate on null-terminated
strings.
.sp
.LP
The \fBindex()\fR function returns a pointer to the first occurrence of
character \fIc\fR in string \fIs\fR.
.sp
.LP
The \fBrindex()\fR function returns a pointer to the last occurrence of
character \fIc\fR in string \fIs\fR.
.sp
.LP
Both \fBindex()\fR and  \fBrindex()\fR return a null pointer if \fIc\fR does
not occur in the string. The null character terminating a string is considered
to be part of the string.
.SH USAGE
.sp
.LP
On most modern computer systems, you can \fInot\fR use a null pointer to
indicate a null string.  A null pointer is an error and results in an abort of
the program.  If you wish to indicate a null string, you must use a pointer
that points to an explicit null string.  On some machines and with some
implementations of the C programming language, a null pointer, if dereferenced,
would yield a null string.  Though often used, this practice is not always
portable. Programmers using a null pointer to represent an empty string should
be aware of this portability issue.  Even on machines where dereferencing a
null pointer does not cause an abort of the program, it does not necessarily
yield a null string.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR bstring (3C),
.BR malloc (3C),
.BR string (3C),
.BR attributes (7),
.BR standards (7)
